通过JDBC连接数据库（三）

通过单例创建JDBCUtil

package com.huawei;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * @author zhangzhao
 *
 * 2012-2-17下午08:53:27
 */
public final class JDBCUtil2 {
	private  String url="jdbc:mysql://localhost:3306/jdbc";
	private  String user="root";
	private  String password="root";
	private static JDBCUtil2 instance=null;
	private JDBCUtil2()
	{
		
	}
	public static JDBCUtil2 getInstance(){
		if(instance==null){
			//懒加载（延时加载，用的时候才去加载）
			synchronized (JDBCUtil2.class) {
				if(instance==null){
				instance=new JDBCUtil2();//第一次加锁
				}
			}
			
		}
		return instance;
	}
	static{
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	public  Connection getConnection() throws SQLException{
		return DriverManager.getConnection(url, user, password);
	}
	public  void free(ResultSet rs,PreparedStatement pStatement,Connection conn){
		
		try {
			if(rs!=null){
				rs.close();
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally{
			try {
				if(pStatement!=null)
					pStatement.close();
			} catch (Exception e2) {
				// TODO: handle exception
			}
			finally{
				if(conn!=null)
					try {
						conn.close();
					} catch (SQLException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
			}
			
		}
		
	}


}